<?php
/*
 * Copyright 2012 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * Credentials object used for OAuth 2.0 Signed JWT assertion grants.
 *
 * @author Chirag Shah <chirags@google.com>
 */
class Google_AssertionCredentials
{
    const MAX_TOKEN_LIFETIME_SECS = 3600;
    public $serviceAccountName;
    public $scopes;
    public $privateKey;
    public $privateKeyPassword;
    public $assertionType;
    public $prn;
  /**
   * @param $serviceAccountName
   * @param $scopes array List of scopes
   * @param $privateKey
   * @param string $privateKeyPassword
   * @param string $assertionType
   * @param bool|string $prn The email address of the user for which the
   *               application is requesting delegated access.
   */
  public function __construct(
      $serviceAccountName,
      $scopes,
      $privateKey,
      $privateKeyPassword = 'notasecret',
      $assertionType = 'http://oauth.net/grant_type/jwt/1.0/bearer',
      $prn = false)
  {
      $this->serviceAccountName = $serviceAccountName;
      $this->scopes = is_string($scopes) ? $scopes : implode(' ', $scopes);
      $this->privateKey = $privateKey;
      $this->privateKeyPassword = $privateKeyPassword;
      $this->assertionType = $assertionType;
      $this->prn = $prn;
  }
    public function generateAssertion()
    {
        $now = time();
        $jwtParams = array(
          'aud' => Google_OAuth2::OAUTH2_TOKEN_URI,
          'scope' => $this->scopes,
          'iat' => $now,
          'exp' => $now + self::MAX_TOKEN_LIFETIME_SECS,
          'iss' => $this->serviceAccountName,
    );
        if ($this->prn !== false) {
            $jwtParams['prn'] = $this->prn;
        }

        return $this->makeSignedJwt($jwtParams);
    }
  /**
   * Creates a signed JWT.
   * @param array $payload
   * @return string The signed JWT.
   */
  private function makeSignedJwt($payload)
  {
      $header = array('typ' => 'JWT', 'alg' => 'RS256');
      $segments = array(
      Google_Utils::urlSafeB64Encode(json_encode($header)),
      Google_Utils::urlSafeB64Encode(json_encode($payload)),
    );
      $signingInput = implode('.', $segments);
      $signer = new Google_P12Signer($this->privateKey, $this->privateKeyPassword);
      $signature = $signer->sign($signingInput);
      $segments[] = Google_Utils::urlSafeB64Encode($signature);

      return implode('.', $segments);
  }
}
